Unlicensed Mobile Access (UMA) allows for access to a GSM core network by means of Wireless LAN (WLAN) or by means of Bluetooth. The UMA standard is developed by the UMA Technology Group (www.umatechnology.org). The UMA standard is since adopted by 3GPP and further developed under the name Generic Access Network (GAN); however, the term UMA is more commonly used than GAN. UMA is specified in 3GPP TS 43.318 and in 3GPP TS 44.318.
Dual mode handsets containing both GSM radio and WLAN radio may access the GSM core network through GSM Radio Access Network (RAN) or through WLAN. WLAN access to the GSM core network may be used at a subscriber's home, in a subscriber's office and near designated public WLAN access points.
Recently in The Netherlands, the “At Home” service (@home; also known as ‘Unique’) has been launched. Subscribers of the @home service use a dual mode handset (GSM access and UMA access) for telecommunication services, and are referred to as GSM/UMA subscribers. Instead of GSM, UMTS may be used in combination with UMA access. In that case, subscribers will be referred to as UMTS/UMA subscribers. Below, the GSM/UMA or UMTS/UMA subscribers are simply referred to as ‘UMA-subscribers’ or just ‘subscribers’. The following rules with respect to numbering are applied by the provider of the @home service:                the subscriber may be contacted on her Mobile Subscriber ISDN Number (MSISDN), irrespective of the location where she is and irrespective of the access through which she is currently registered with the MSC;        the subscriber also has a geographic number assigned to her; this geographic number forms part of the Public Switched Telephone Network (PSTN) fixed network numbering plan. She may be contacted on that number only when she is attached to the GSM network via a WLAN access point.        
In a co-pending application PCT/NL2006/050279 filed in the name of the same applicant, a method is described that ensures that calls that are directed to the subscriber's geographic number are delivered to that subscriber only when she is registered to the MSC through WLAN access at that moment. The solution described in PCT/NL2006/050279 entails the following aspects:                when the subscriber is registered to the MSC through WLAN access, this is marked in a subscriber database of the operator;        when a call is established to the subscriber using the geographic number, the call is handled in the PSTN and an Intelligent Network (IN) service is triggered in the PSTN;        the PSTN checks whether the subscriber is currently attached via WLAN; if yes, then the IN service connects the call to the subscriber's MSISDN; otherwise, the IN service forwards the call to voicemail.In the method described above special IN handling is required in the PSTN even though the call is actually destined for a GSM network subscriber. Furthermore, number translation needs to be done. As a result, once the call arrives at the GSM network, it is no longer known whether the subscriber was called on her MSISDN or on her geographic number. Also, a special @home location server is required.        
A goal of the present invention is to improve the method described above.
This goal is achieved by providing a method of routing a call made to a fixed telephone number of a UMA-subscriber, according to one or more of the claims. In a particular embodiment the telecommunications network further comprises a Signalling Relay Function (SRF), wherein the first switching node:
receives an ISUP IAM message from a third switching node, the ISUP IAM message comprising a called party number comprising the fixed telephone number and a routing prefix;
sends a MAP SRI message to the location server;
receives subscription information and location information from the location server;
sends a trigger message to the service control entity, using the received subscription information, the trigger message comprising the location information, and wherein the SRF:
stores a list comprising a fixed number and an associated location server for the UMA-subscriber;
receives a MAP SRI message from the first switching node, the MAP SRI message comprising the fixed telephone number;
forwards the MAP SRI message to the location server associated with the fixed telephone number using the list;
receives a MAP SRI result message from the location server, the MAP SRI result message containing subscription information and location information of the subscriber;
forwards the subscription information and location information to the first switching node.
The advantages of this SRF are that by provisioning a fixed number in the SRF and associating with this fixed number an address of a location server (i.e. HLR), this fixed number may practically be treated as an MSISDN. Terminating call handling for calls to a UMA-subscriber may be generic for the following two cases:                (1) the UMA-subscriber is publicly known by a fixed number (‘fixed number’ being a number belonging to a number range that is originally allocated to fixed (land line) telephones);        (2) the UMA-subscriber is publicly known by a mobile number (‘mobile number’ being a number belonging to a number range that is originally allocated to mobile (cellular) telephones);        
A subscriber of this mobile telecommunication network may have a fixed number and a mobile number associated with her, whilst having one mobile phone, one subscription and one set of service data.
In another embodiment, the mobile telecommunications network further comprises a service control entity, which:
runs an IN service;
receives location information of a UMA-subscriber comprised in an IN trigger message; and
uses the location information for its service logic processing.
If the subscriber is found to be under UMA access, a home zone indicator can be placed in a Call Detail Record, wherein the home zone indicator indicates to a billing system that the rate of the call must be adapted. The IN service may be a prepaid service or a VPN service. The charging of the call will not just be based on the location of the called subscriber, but also on the number by means of which this subscriber was called. That is a specific enhancement to prepaid and VPN service logic handling, compared to current methodology.
Such a method may be implemented in a network without impacting the GSM core network entities. There are no requirements for enhanced Signaling relay function.
Further, in one or more embodiments, the claimed method may be applied without the need for invoking a dedicated IN service. It may be used in combination with existing IN service such as prepaid or VPN.
Further, in one or more embodiments of the method, the second switching node may apply for example adapted ring signal when the destination subscriber is under UMA access and is called on her (the subscriber's) fixed number.
In yet a further aspect, the invention relates to a service control entity for providing intelligent network services to users of a mobile telecommunications network.
The invention also relates to a service control entity for providing intelligent network services to users of a mobile telecommunications network.
The invention also relates to a switching node for use in a mobile telecommunications network.
Furthermore, the invention relates to a location server for use in a mobile telecommunications network.
Finally, in one or more embodiments, the invention relates to a computer program product comprising computer executable code, which when loaded on a computer system, allows the computer system to execute the method as described above.